Pretty sure the airtight casing is here on purpose to trap flammables gas a dying cell create. Without it it would be very unsafe to use this type of batteries.
I guess using cylindrical cells in power tools, laptops, electric bikes and cars, power banks, flashlights, etc. must be super unsafe then, since they all have valves that release gas instead of inflating.
A container that traps flammable gasses is called a bomb
This is not usually a design goal
No, a container that contains flammable gasses and then destructively allows them to escape is a bomb, one that just inflates is arguably the equivalent of a self inflating pillow.
Gasses create pressure
A phone casing is not a pressure vessel
This isn’t going to work